This invention relates to plasticized polyvinyl butyral (PVB) and more particularly PVB sheet containing compatible plasticizer.
Plasticized PVB sheet is used in light-transmitting laminates containing one or more rigid layers, such as glass, for applications such as building and vehicle windows, show cases, protective glass for pictures, documents and the like. The plasticized sheet absorbs energy and prevents disintegration when, for example, the head of a vehicle occupant strikes the rigid layer of a laminate window after a sudden stop or a foreign object is propelled against the outside of the laminate. The PVB resin contains hydroxyl groups in the polymer chain to promote adhesion to glass.
The plasticizer must be carefully chosen to contribute to a balance of performance properties in the laminate. Cost/benefit performance continues of importance in assessing plasticized PVB for safety laminates having valuable commercial properties.
Now plasticized PVB formulations have been developed exhibiting improved plasticizer and PVB compatibility (affinity of resin and plasticizer for each other) in comparison with prior art systems.
Accordingly, a principal object of this invention is to provide plasticized PVB formulations exhibiting improved compatibility of plasticizer with PVB resin.
Another object is to provide a compatible plasticized PVB formulation wherein the plasticizer is synthesized from readily available, relatively inexpensive starting materials.
These objects are achieved by polyvinyl butyral resin having a hydroxyl content of less than 19.5, preferably about 17 to 19 weight % calculated as polyvinyl alcohol plasticized with a compatible amount of triethylene glycol di-2-ethylhexanoate (3GEH).
Also provided is a sheet formed of this composition.